Protection circuit

ABSTRACT

A protection circuit, comprising: a transient suppression circuit, configured to suppress a transient voltage; and a short-circuit protection circuit connected between the transient suppression circuit and a ground terminal, wherein when the transient suppression circuit is shorted out and the transient voltage is a protection voltage, the short-circuit protection circuit disconnects a loop where the transient suppression circuit is located. The short-circuit protection circuit has a turned-on state and a turned-off state; the short-circuit protection circuit is in a turned-on state when the transient suppression circuit is shorted out and the transient voltage is greater than the protection voltage; and the short-circuit protection circuit is in a turned-off state when the transient suppression circuit is shorted out and the transient voltage is a protection voltage.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a US national stage of PCT International ApplicationNo. PCT/CN2018/117760 filed on Nov. 27, 2018 and entitled “PROTECTIONCIRCUIT,” which claims priority to Chinese Patent Application No.2018215009267, filed with the Chinese Patent Office on Sep. 13, 2018 andentitled “PROTECTION CIRCUIT,” which is incorporated herein by referencein its entirety.

TECHNICAL FIELD

This application relates to the field of circuit protectiontechnologies, and in particular, to a protection circuit.

BACKGROUND

The description herein provides only background information related tothis application, but does not necessarily constitute the exemplarytechnology.

Currently, a transient inverter circuit is disposed in some circuits,which is mainly configured to prevent a surge current introduced whenthe power grid is unstable from burning elements. When the transientinverter circuit is subjected to an overshoot voltage, it changes highresistance at its two ends to low resistance at an extremely high speedto protect the circuits connected subsequently from being damaged.However, when the transient inverter circuit is burnt to beshort-circuited, it cannot continue protecting the subsequent circuits.

SUMMARY

According to various embodiments of this application, a protectioncircuit is provided.

A protection circuit includes:

a transient suppression circuit configured to suppress a transientvoltage; and

a short-circuit protection circuit connected between the transientsuppression circuit and a ground terminal,

wherein the short-circuit protection circuit disconnects a loop wherethe transient suppression circuit is located when the transientsuppression circuit is short-circuited and the transient voltage is aprotection voltage.

In the protection circuit described above, a short-circuit protectionunit is disposed between a transient suppression unit and the groundterminal, and the short-circuit protection unit can disconnect the loopwhere the transient suppression unit is located when the transientsuppression unit is short-circuited and the transient voltage is theprotection voltage, that is, disconnect the protection circuit, and theprotection circuit will not act on an input signal, thereby avoiding ashort-circuit of the protected signal to the ground and ensuring thenormal operation of subsequent circuits.

A protection circuit includes:

a transient suppression circuit configured to suppress an inputtransient voltage within a protection voltage; and

a short-circuit protection circuit connected between the transientsuppression circuit and a ground terminal,

wherein: the short-circuit protection circuit includes a firstvoltage-dividing circuit, a second voltage-dividing circuit and aswitching circuit; the first voltage-dividing circuit and the secondvoltage-dividing circuit are sequentially connected in series betweenthe transient suppression circuit and the ground terminal; a controlterminal of the switching circuit is connected between the firstvoltage-dividing circuit and the second voltage-dividing circuit; aninput terminal of the switching circuit is connected to the transientsuppression circuit; an output terminal of the switching circuit isconnected to the ground terminal; the first voltage-dividing circuit andthe second voltage-dividing circuit cooperatively control the switchingcircuit to be in an on state when the transient suppression circuit isshort-circuited and the transient voltage is greater than the protectionvoltage, and to be in an off state when the transient suppressioncircuit is short-circuited and the transient voltage is the protectionvoltage.

Details of one or more embodiments of this application are provided inthe following accompanying drawings and descriptions. Other features,objectives, and advantages of this application will become apparent fromthe specification, the accompanying drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

To describe the technical solutions of the embodiments of thisapplication or the exemplary technology more clearly, the followingbriefly introduces the accompanying drawings required for describing theembodiments or the exemplary technology. Apparently, the accompanyingdrawings in the following description show only some embodiments of thisapplication, and persons of ordinary skill in the art may still deriveother drawings from these accompanying drawings without creativeefforts.

FIG. 1 is a block diagram of a protection circuit in an embodiment.

FIG. 2 is a block diagram of a short-circuit protection circuit in anembodiment.

FIG. 3 is a circuit diagram of a protection circuit in an embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

To make the objectives, technical solutions, and advantages of thisapplication clearer and more comprehensible, the following furtherdescribes this application in detail with reference to the accompanyingdrawings and embodiments. It should be understood that the specificembodiments described herein are merely used to explain this applicationbut are not intended to limit this application.

In the description of this application, it should be understood thatorientation or position relationships indicated by the terms such as“center”, “transverse”, “on”, “below”, “left”, “right”, “vertical”,“horizontal”, “top”, “bottom”, “inside”, and “outside” are based onorientation or position relationships shown in the accompanyingdrawings, and are used only for ease and brevity of illustration anddescription, rather than indicating or implying that the mentionedapparatus or component must have a particular orientation or must beconstructed and operated in a particular orientation. Therefore, suchterms should not be construed as limiting of this application. Inaddition, it should be noted that when an element is referred to asbeing “formed on” another element, it can be directly connected to theanother element or intervening elements may also be present. When anelement is referred to as being “connected” to another element, it canbe directly connected to the another element or intervening elements mayalso be present. In contrast, when an element is referred to as being“directly connected” to another element, there are no interveningelements present.

In an embodiment, as shown in FIG. 1, a protection circuit includes atransient suppression circuit 12 and a short-circuit protection circuit14. The short-circuit protection circuit 14 is connected in seriesbetween the transient suppression circuit 12 and a ground terminal. Thetransient suppression circuit 12 is configured to suppress a transientvoltage so as to prevent subsequent circuits from being disturbed by atransient high voltage higher than a protection voltage and causing thecircuits to be damaged. The short-circuit protection circuit 14 isconfigured to disconnect a loop where the transient suppression circuit12 is located when the transient suppression circuit 12 is destroyed tobe short-circuited and the transient voltage is the protection voltage.

Specifically, in the case of the normal operation of the transientsuppression circuit 12, when the transient voltage is greater than theprotection voltage, the transient suppression circuit 12 is reverselybroken down with its impedance being abruptly lowered at an extremelyhigh speed, while absorbing a large current and clamping a voltageacross its two ends at a predetermined value, thereby ensuring thefollowing circuit elements from being damaged by the impact of transienthigh energy, to protect the subsequent circuits. When the transient highvoltage disappears, the transient suppression circuit 12 returns to ahigh impedance state again. When impacted by another transient highvoltage, the transient suppression circuit 12 repeats the operationdescribed above. When the transient voltage is the protection voltage,the transient suppression circuit 12 appears as being in the highimpedance state, which will not affect the normal operation of thenormally operating system of the subsequent circuits. Therefore, thesetting of the protection voltage can be realized by configuring thetransient suppression circuit 12. When the transient voltage is greaterthan the protection voltage, the transient suppression circuit 12appears as being in a low impedance state, thereby forming a loopdischarging, and further enabling the voltage loaded into the subsequentcircuits, that is, the protected circuit, to be within the protectionvoltage, thus realizing the protection of the subsequent circuits. Whenthe transient voltage is the protection voltage, the transientsuppression circuit 12 appears as being in the high impedance state,which will not affect the normal operation of subsequent circuits.

When the elements in the transient suppression circuit 12 are damaged tobe short-circuited, the short-circuit protection circuit 14 plays aprotective role to ensure the normal operation of subsequent circuits.Specifically, the short-circuit protection circuit 14 is configured tocontrol the loop where the transient suppression circuit 12 is locatedto be disconnected when the transient suppression circuit 12 isdestroyed to be short-circuited and the transient voltage is theprotection voltage, thereby preventing the protected signal from beingshort-circuited to the ground and ensuring the normal operation ofsubsequent circuits.

Optionally, in an embodiment, the short-circuit protection circuit 14has two states including an on state and an off state. In the case whereelements in the transient suppression circuit 12 are not damaged, whenthe transient voltage is the protection voltage, the elements in thetransient suppression circuit 12 may not be reversely broken down. Atthis time the transient suppression circuit 12 is equivalent to an opencircuit and the transient suppression circuit 12, the short-circuitprotection circuit 14 do not operate, and the system operates normally.When the transient high voltage is greater than the protection voltage,the elements in the transient suppression circuit 12 are reverselybroken down, and the impedance of the transient suppression circuit 12abruptly drops. At this time, the short-circuit protection circuit 14 isin the on state, thereby causing the loop where the transientsuppression circuit 12 is located to absorb a large current and to playa role of clamping the voltage, thus playing the role of protecting thefollowing circuit elements.

The transient suppression circuit 12 may be damaged by of a high voltagefor a long time or an instantaneous excessively high voltage, and mayappear as being in a short-circuit state. When the transient voltage isthe protection voltage, the short-circuit protection circuit 14 is inthe off state, thereby ensuring that the input normal signal will notpass through the loop where the transient suppression circuit 12 in theshort-circuit state is located and the system operates normally. Whenthe transient voltage is greater than the protection voltage, theshort-circuit protection circuit 14 is in an on state, thereby ensuringthat the transient high voltage passes through the loop where thetransient suppression circuit 12 is located, so as to avoid the impactof the transient high voltage on the subsequent circuit elements andensure the normal operation of the subsequent circuit.

Optionally, in an embodiment, as shown in FIG. 2, the short-circuitprotection circuit 14 includes a first voltage-dividing circuit 140, asecond voltage-dividing circuit 142 and a switching circuit 144. Thefirst voltage-dividing circuit 140 and the second voltage-dividingcircuit 142 are sequentially connected in series between the transientsuppression circuit 12 and the ground terminal. The control terminal 148of the switching circuit 144 is connected between the firstvoltage-dividing circuit 140 and the second voltage-dividing circuit142, the input terminal 146 is connected to the transient suppressioncircuit 12, and the output terminal 149 is connected to the groundterminal. The first voltage-dividing circuit 140 and the secondvoltage-dividing circuit 142 cooperate to control the switching circuit144 to be in the on state when the transient suppression circuit 12 isshort-circuited and the transient voltage is greater than the protectionvoltage, and to be in the off state when the transient suppressioncircuit 12 is short-circuited and the transient voltage is theprotection voltage.

Specifically, in an embodiment, the first voltage-dividing circuit 140includes a first resistor R1 and the second voltage-dividing circuit 142includes a second resistor R2, as shown in FIG. 3. In anotherembodiment, the first voltage-dividing circuit 140 may also be aresistor circuit consisting of two or more resistors connected in seriesor in parallel. Likewise, the second voltage-dividing circuit 142 may bea resistor circuit consisting of two or more resistors connected inseries or in parallel, which is not limited to this embodiment.

In another embodiment, the switching circuit 144 is a PMOS transistorT1. A gate of the PMOS transistor T1 operates as the control terminal148 of the switching circuit 144, a source of the PMOS transistor T1operates as the input terminal 146 of the switching circuit 144, and adrain of the PMOS transistor T1 operates as the output terminal 149 ofthe switching circuit 144, as shown in FIG. 3.

Optionally, in an embodiment, a threshold voltage of the PMOS transistorT1 is −0.6V, that is, when the voltage between the gate and the drain ofthe PMOS transistor T1 is greater than −0.6V, the PMOS transistor T1 isin an on state, otherwise in an off state. A ratio between resistancesof the first voltage-dividing circuit 140 and the secondvoltage-dividing circuit 142 is 1 to 7. Assuming a TTL high level of3.3V to be protected, when the elements in the transient suppressioncircuit 12 are not damaged, the elements in the transient suppressioncircuit 12 will be reversely broken down if the transient voltage isgreater than the protection voltage. Due to the voltage-dividing effectof the first voltage-dividing circuit 140 and the secondvoltage-dividing circuit 142, as long as the voltage loaded onto thesource is greater than 4.2V, the voltage Vgs across the gate and thedrain can be greater than −0.6V, and the PMOS transistor T1 is turned onto form a discharging loop. At this time, the transient suppressioncircuit 12 is reversely broken down with its impedance being abruptlylowered at an extremely high speed, while absorbing a large current andclamping the voltage across its two ends at a predetermined value,thereby ensuring the following circuit elements from being damaged bythe impact of transient high energy to protect the circuits. When thetransient voltage disappears, the transient suppression circuit 12returns to a high impedance state again. When impacted by anothertransient voltage, the transient suppression circuit 12 repeats theoperation described above. When the transient voltage is the protectionvoltage, the transient suppression circuit 12 appears as being in thehigh impedance state, which will not affect the normal operation of thenormally operating system of the subsequent circuits.

When the elements in the transient suppression circuit 12 are damaged,if the transient voltage is greater than the protection voltage, thevoltage Vgs across the gate and the drain of the PMOS transistor T1 canbe greater than −0.6V due to the voltage-dividing effect of the firstvoltage-dividing circuit 140 and the second voltage-dividing circuit142, and the PMOS transistor T1 is turned on, thereby ensuring thetransient high voltage to pass through the loop where the transientsuppression circuit 12 is located, to avoid the impact of the transienthigh voltage on subsequent circuit elements and ensuring the normaloperation of subsequent circuits. If the transient voltage is theprotection voltage, the conduction condition of the PMOS transistor T1cannot be reached at this time and the PMOS transistor T1 is turned off.And since the PMOS transistor T1 cannot be turned on, the short-circuitprotection circuit 14 is in the off state, thus ensuring that the inputnormal signal will not pass through the loop where the transientsuppression circuit 12 in the short-circuit state is located and thesystem operates normally.

In an embodiment, the transient suppression circuit 12 includes asteering diode array and a voltage regulator diode. The steering diodearray consists of eight transient suppression diodes (D2-D9) every twoof which are connected in series with each other and then connected inparallel. The voltage regulator diode and the steering diode array areconnected in parallel to form a transient suppression circuit 12. Theinput terminal 16 is connected to the power or the ground. Theprotection circuit may have four input terminals, including inputterminals 100, 102, 104, and 106, that is, this circuit can protectmultiple input signals at the same time. The steering diode can protectthe input signal 10 whether it is a positive signal or a negativesignal. For example, when a positive voltage is input into the inputterminal 102, the current flows to the diode D2, and when a negativevoltage is input into the input terminal 102, the current flows to thediode D3.

In an embodiment, the above-described transient suppression circuit 12is a transient suppression chip, that is, the steering diode array andthe voltage regulator diode D1 are packaged together.

In an embodiment, the short-circuit protection circuit 14 may beintegrated inside the transient suppression chip described above. Atthis time, the protection circuit operates as an independent transientsuppression chip (TVS).

Technical features in the foregoing embodiments may be combinedrandomly. For the brevity of description, not all possible combinationsof various technical features in the foregoing embodiments aredescribed. However, as long as combinations of these technical featuresdo not contradict each other, it should be considered that thecombinations all fall within the scope of this specification.

The foregoing embodiments only show several implementations of thisapplication and are described in detail, but they should not beconstrued as a limit to the patent scope of this application. It shouldbe noted that, persons of ordinary skill in the art may make variouschanges and improvements without departing from the ideas of thisapplication, which shall all fall within the protection scope of thisapplication. Therefore, the protection scope of the patent of thisapplication shall be subject to the appended claims.

What is claimed is:
 1. A protection circuit, comprising: a transient suppression circuit configured to suppress a transient voltage; and a short-circuit protection circuit connected between the transient suppression circuit and a ground terminal, wherein the short-circuit protection circuit disconnects a loop where the transient suppression circuit is located when the transient suppression circuit is short-circuited and the transient voltage is a protection voltage; wherein the short-circuit protection circuit comprises a first voltage-dividing circuit, a second voltage-dividing circuit and a switching circuit; the first voltage-dividing circuit and the second voltage-dividing circuit are sequentially connected in series between the transient suppression circuit and the ground terminal; a control terminal of the switching circuit is connected between the first voltage-dividing circuit and the second voltage-dividing circuit; an input terminal of the switching circuit is connected to the transient suppression circuit; an output terminal of the switching circuit is connected to the ground terminal; and the first voltage-dividing circuit and the second voltage-dividing circuit cooperatively control the switching circuit to be in the on state when the transient suppression circuit is short-circuited and the transient voltage is greater than the protection voltage, and to be in the off state when the transient suppression circuit is short-circuited and the transient voltage is the protection voltage; the switching circuit comprises a PMOS transistor; a gate of the PMOS transistor operates as the control terminal; a source of the PMOS transistor operates as the input terminal; and a drain of the PMOS transistor operates as the output terminal; and the PMOS transistor has a threshold voltage of −0.6 volt; and a ratio between resistances of the first voltage-dividing circuit and the second voltage-dividing circuit is 1:7.
 2. The protection circuit according to claim 1, wherein the first voltage-dividing circuit comprises a first resistor.
 3. The protection circuit according to claim 1, wherein the second voltage-dividing circuit comprises a second resistor.
 4. The protection circuit according to claim 1, wherein: the transient suppression circuit comprises a steering diode array and a voltage regulator diode; the steering diode array comprises eight transient suppression diodes; every two of the eight transient suppression diodes are connected in series with each other and then connected in parallel; the voltage regulator diode is connected in parallel with the steering diode array; and the short-circuit protection circuit is connected in series with the voltage regulator diode and is grounded.
 5. The protection circuit according to claim 4, wherein: the protection circuit comprises a plurality of signal input terminals, and the signal input terminals are disposed between the every two transient suppression diodes connected in series with each other; and the signal input terminals are configured to input an input signal to the protection circuit.
 6. The protection circuit according to claim 5, wherein the input signal is a voltage signal.
 7. The protection circuit according to claim 1, wherein the transient suppression circuit is a transient suppression chip.
 8. The protection circuit according to claim 7, wherein the short-circuit protection circuit is integrated within the transient suppression chip.
 9. A protection circuit, comprising: a transient suppression circuit configured to suppress an input transient voltage within a protection voltage; and a short-circuit protection circuit connected between the transient suppression circuit and a ground terminal, wherein: the short-circuit protection circuit comprises a first voltage-dividing circuit, a second voltage-dividing circuit and a switching circuit; the first voltage-dividing circuit and the second voltage-dividing circuit are sequentially connected in series between the transient suppression circuit and the ground terminal; a control terminal of the switching circuit is connected between the first voltage-dividing circuit and the second voltage-dividing circuit; an input terminal of the switching circuit is connected to the transient suppression circuit; an output terminal of the switching circuit is connected to the ground terminal; the first voltage-dividing circuit and the second voltage-dividing circuit cooperatively control the switching circuit to be in an on state when the transient suppression circuit is short-circuited and the transient voltage is greater than the protection voltage, and to be in an off state when the transient suppression circuit is short-circuited and the transient voltage is the protection voltage; the switching circuit comprises a PMOS transistor; a gate of the PMOS transistor operates as the control terminal; a source of the PMOS transistor operates as the input terminal; and a drain of the PMOS transistor operates as the output terminal; and the PMOS transistor has a threshold voltage of −0.6 volt; and a ratio between resistances of the first voltage-dividing circuit and the second voltage-dividing circuit is 1:7.
 10. The protection circuit according to claim 9, wherein: the transient suppression circuit comprises a steering diode array and a voltage regulator diode; the steering diode array comprises eight transient suppression diodes; every two of the eight transient suppression diodes are connected in series with each other and then connected in parallel; the voltage regulator diode is connected in parallel with the steering diode array; and the short-circuit protection circuit is connected in series with the voltage regulator diode and is grounded.
 11. The protection circuit according to claim 10, wherein: the protection circuit comprises a plurality of signal input terminals, and the signal input terminals are disposed between the every two transient suppression diodes connected in series with each other; and the signal input terminals are configured to input an input signal to the protection circuit.
 12. The protection circuit according to claim 11, wherein the input signal is a voltage signal. 